I'm not sure if "Turbo Surge" is the proper term to describe my condition, but I don't know what else to call it. I'm motoring along in 5th gear doing, say, 70 mph. Holding it steady, no pedal action, no cruise control, when all of a sudden I get a momentary surge, or lunge, and then back to normal. No visible change in either mph or rpms, but the turbo needle does flutter up and back during the surge. Or lunge. Or whatever. It's not a constant condition and I can't necessarily replicate it. Sometimes it happens, sometimes it don't.
Idle is good and the car, with about 80k on it, runs tip-top in all other respects, although I have - once - detected a slight hiccup while going downhill, 40 mph-ish, in third gear. Related? Beats me.
The car is new-to-me, by the way, but the previous owner is a friend/co-worker who has always maintained the vehicle by the book, with oil changes every 3k. She noted the condition once, many miles ago, but never again. Any thoughts or suggestions?
Much obliged,
Michael